Grendell argues police didn't wait for a negotiator trained to handle mental health crises and failed to obtain a proper warrant to use a bomb. Eighteen state police members and one member of the attorney general's office are named as defendants.

The explosive was used to draw Grendell out of his house after an extended standoff when he had fired at police officers, authorities said.

A spokesman for the attorney general's office, which is representing the state police, declined to comment on the lawsuit.

The blast destroyed part of his home, and Grendell was shot three times when he emerged with a rifle.

"No reasonable officer or supervisor could have concluded that robot/bombing Michael Grendell's home and person and then shooting him in his further disabled state, were in any way constitutionally or legally justified," the lawsuit reads.

Grendell seeks financial damages and asks the state to cover his medical expenses, lost wages and attorney fees. Grendell filed a notice in December saying he would seek $120 million in damages, and his lawsuit requests a jury trial to assess his claims.

Last year, Grendell was sentenced to probation and a suspended jail term on charges, including criminal threatening with a dangerous weapon. Under the agreement, an attempted murder charge was dropped and Grendell was sentenced to 38 days, the amount of time he already spent at a state psychiatric hospital.

Grendell was psychotic and delusional at the time of the episode, a forensic psychologist testified at the time. He spent two months in the hospital, used a feeding tube and has since been diagnosed with a depressive disorder with psychotic features.

The newspaper reports the June 2018 standoff in Dixmont is believed to be the first time Maine police ended a standoff by using a robot to deliver an explosive.

The case raised questions about the police's military-style tactics against a man in the throes of a mental health crisis. The roof collapsed after the explosion blew out the first floor of his home, leaving just a concrete slab remaining.